1. Technical Field
This invention relates to galvanic cathodic protection of embedded steel in concrete and the like. Specifically, to sacrificial anodes electrically linked to the steel reinforcement.
2. Description of Prior Art
Prior art devices of this type have relied on sacrificial anodes to address the issue of steel reinforcement corrosion which can and will occur due to the inherent porous nature of the concrete in which it is embedded. Such corrosion occurs when the concrete becomes contaminated with, for example, chloride ions from structural exposure to nature and user applied salt or carbonation due to carbon dioxide penetration into the concret and loosing therefore its protective alkalinity. Once this occurs, the reinforcement steel will corrode increasing its volume causing accelerated failures of the surrounding concrete structure. By the use of the electrically connected sacrificial anode connected to the reinforcement steel cathodic protection is achieved, reducing or eliminating the corrosion of the steel by making it the cathode of the electric chemical cell.
Galvanic cathodic protection using sacrificial anodes such as zinc and aluminum which have inherently negative electro chemical potentials establishes a passive protective current flow which is well known and understood in the art, see for example U.S. Pat. Nos. 4,435,263, 5,292,411, 6,022,469, 6,033,553, 6,165,346, 6,562,229, 6,572,760, 7,160,433 and 7,488,410.
In U.S. Pat. No. 4,435,263, a back fill composition for magnesium galvanic anodes is disclosed using calcium sulphite, bentonite and one compound from a group of sodium alkylates and sodium dialkyldithiocarbamates.
U.S. Pat. No. 5,292,411 is directed to a method of patching eroded concrete using a metal anode with an ionically conductive hydrogel attached to a portion of the anode being in elongated folded form.
U.S. Pat. No. 6,022,469 discloses a method by which a zinc or zinc alloyed anode is set in mortar that maintains a high PH to provide passification of the zinc anode maintaining same in an electro chemical active state.
U.S. Pat. No. 6,033,533 discloses the most effective humectants, debquescent or hydroscopic chemicals, lithium, nitrate and lithium bromine respectively to maintain a galvanic sprayed anode in active state.
U.S. Pat. No. 6,165,346 also claims a use of deliquescent chemicals to enhance the performance of the galvanic anodes.
U.S. Pat. No. 6,562,229 is drawn to a louvered metal anode with an electrocatalytically active coating on a substrate.
U.S. Pat. No. 6,572,760 illustrated the use of deliquescent material bound into a porous anode body to maintain the anodes electro chemical active properties.
U.S. Pat. No. 7,160,433 claims a cathodic protection system in which zinc anode embedded in mortar in which a humeclant is employed to impart high ionic conductivity.
Finally, U.S. Pat. No. 7,488,410 shows an anode assembly for cathodic protection using an anode covered with an ionically conductive material having an electro chemical activating agent configured to conform closely to the steel reinforcing bar in which it adjacently protects.